A cache is a least recently used (LRU) list of cache items, accessed via \fClong\fR keys. Each cache item has a cost. The sum of item costs, totalCost(), will not exceed the maximum cache cost, maxCost(). If inserting a new item would cause the total cost to exceed the maximum cost, the least recently used items in the cache are removed.
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Apart from insert(), by far the most important function is find() (which also exists as operator[]). This function looks up an item, returns it, and by default marks it as being the most recently used item.
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There are also methods to remove() or take() an object from the cache. Calling setAutoDelete(TRUE) for a cache tells it to delete items that are removed. The default is to not delete items when they are removed (i.e. remove() and take() are equivalent).
When inserting an item into the cache, only the pointer is copied, not the item itself. This is called a shallow copy. It is possible to make the cache copy all of the item's data (known as a deep copy) when an item is inserted. insert() calls the virtual function TQPtrCollection::newItem() for the item to be inserted. Inherit a dictionary and reimplement newItem() if you want deep copies.
Constructs a cache whose contents will never have a total cost greater than \fImaxCost\fR and which is expected to contain less than \fIsize\fR items.
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\fIsize\fR is actually the size of an internal hash array; it's usually best to make it prime and at least 50% bigger than the largest expected number of items in the cache.
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Each inserted item is associated with a cost. When inserting a new item, if the total cost of all items in the cache will exceed \fImaxCost\fR, the cache will start throwing out the older (least recently used) items until there is enough room for the new item to be inserted.
Removes all items from the cache and then destroys the int cache. If auto-deletion is enabled the cache's items are deleted. All iterators that access this cache will be reset.
Returns the item associated with \fIk\fR, or 0 if the key does not exist in the cache. If \fIref\fR is TRUE (the default), the item is moved to the front of the least recently used list.
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If there are two or more items with equal keys, the one that was inserted most recently is returned.
Inserts the item \fId\fR into the cache with key \fIk\fR and assigns it a cost of \fIc\fR (default 1). Returns TRUE if it succeeds; otherwise returns FALSE.
\fBWarning:\fR If this function returns FALSE (for example, the cost \fC,\fR exceeds maxCost()), you must delete \fId\fR yourself. Additionally, be very careful about using \fId\fR after calling this function. Any other insertions into the cache, from anywhere in the application or within TQt itself, could cause the object to be discarded from the cache and the pointer to become invalid.
Returns the item associated with \fIk\fR, or 0 if \fIk\fR does not exist in the cache, and moves the item to the front of the least recently used list.
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If there are two or more items with equal keys, the one that was inserted most recently is returned.
A debug-only utility function. Prints out cache usage, hit/miss, and distribution information using tqDebug(). This function does nothing in the release library.
Takes the item associated with \fIk\fR out of the cache without deleting it, and returns a pointer to the item taken out or 0 if the key does not exist in the cache.
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If there are two or more items with equal keys, the one that was inserted most recently is taken.
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All iterators that refer to the taken item are set to point to the next item in the cache's traversal order.
